This invention relates to desoldering tools in general, and in particular to a desoldering tool with improved power control.
Currently most desoldering in the electronics trade is performed with desoldering systems which consist of an electrical power base and desoldering handpiece. The base typically includes a pump and a transformer and is connected to the desoldering handpiece by an electric cord and a vacuum tube. The base sits on an electronics workbench and the operator holds the desoldering handpiece while working.
An electrical desoldering tool can perform any number of functions. For example, the tool can be used to generate heat at a tip which is applied to circuit board components to melt the bonding solder that holds various components to the board. The tool can also supply a vacuum to draw the molten solder into a reservoir, for example, in the handpiece.
Present desoldering devices are often cumbersome. For example, they require an electric cord to be attached to the gun to energize the heating element. In addition, a vacuum hose must be attached to the gun to remove the melted solder from the circuit board. Both of these appendages must be dragged around by the operator making operation of the desoldering difficult, even for experienced operators. This arrangement further requires that the vacuum pump and transformer be mounted on a bench in the vicinity of the desoldering operation.
The principal disadvantage of the above described arrangement is the lack of mobility and portability as a result of the handpiece being attached to the base by an electrical cord and pneumatic tube. Therefore, according to this arrangement, the operator may only move about 4 to 5 feet from the base. In addition, the nature of the cord and tube make the operation of the device unwieldy.
One method that has been used in an attempt to overcome some of the problems associated with these earlier systems was to manufacture a self contained desoldering gun placing a vacuum pump in the handle of the desoldering gun. According to this arrangement the need for a pneumatic tube connected to the base is eliminated. However, the motors typically used to power the vacuum pump were operated with line voltage motors, which are large and heavy. In addition, these AC electric motors operate at 100 or 120 volts and required significant insulation adding further to the considerable weight of the devices. Consequently, the portable tool itself became large, heavy, and difficult to handle by the operator, especially over extended periods of time.
Another method of manufacturing a self contained desoldering gun provided an improvement over these earlier portable desoldering guns by operating the built-in vacuum pump with a low voltage DC electric motor that is electrically connected in at least partial series with a heating tip. According to this arrangement the heating tip reduces the voltage in the circuit. Subsequently, the size of the motor required to operate the pump and the overall weight of the desoldering gun was reduced. The reduced weight allowed the gun to be more easily handled by operators.
An example of a desoldering gun embodying this arrangement is shown in FIG. 1. Turning to FIG. 1 desoldering gun is referred to in general by numeral 10 and contains the major components of a tip 20, vacuum pump 40, and low voltage DC motor 50. The low voltage DC motor 50 located in the handle of the desoldering gun operates a gun mounted vacuum pump 40. AC line voltage is received through cord 42.
FIG. 2 shows an exemplary circuit diagram corresponding to the desoldering gun of FIG. 1. According to this arrangement, AC line voltage 32 is converted to DC current by rectifier 36 and is reduced in voltage by placing a heating element 34 of the desoldering gun in partial series with the pump motor 50. A portion of the heating element 34 which is not in series with the pump motor 50 is in parallel with the pump motor 50 when the pump motor is energized. Switch 38 is a trigger switch (see FIG. 1) used to energize motor 50 via the series arrangement of switch 38 and motor 50 as shown in FIG. 2.
While this embodiment provided a major improvement over prior desoldering guns, the desoldering gun can be susceptible to electromagnetic interference (EMI) and radio frequency interference (RFI). This arrangement can also result in decreased power associated with use of the motor during operation of the vacuum pump.